This invention relates to a method of producing a cross-fin type heat exchanger, such as a natural convection type radiator or a solar heat collector having heat collecting surfaces formed by bending the fins, and, more particularly, to a method for mechanically producing a heat exchanger of the aforementioned type having a large fin pitch by a continuous process.
A cross-fin type heat exchanger may, for example, be used in a forced circulation type solar heating system wherein a cabinet 1 has a light transmitting member 2, formed of glass, fitted to a front side thereof and a heat insulating layer 3 fitted to a rear side thereof. A heat collecting section 4, in the form of a cross-fin heat exchanger, include an inlet header 5, an outlet header 6, pipes 7, through which a heated medium flows, and fins 8 formed of aluminum, copper, etc., secured to the pipes 7. The fins 8 have a thickness in the range between 0.15 and 0.6 mm and are formed with burred openings through which the pipes 7 extend, after the fins 8 are placed one over another with a spacing interval of about 30 mm. Production of the heat exchanger 4 is completed by expanding the pipes 7 which are spaced apart from one another by a spacing interval of 50-100 mm. The fins 8a on the rear side are bent to provide heat collecting surfaces. FIG. 3 shows the fins 8a being forced by the heat insulating layer 3 into contact with the pipes 7.
The solar heat collector is installed in such a manner that the heat collecting surfaces 8a are disposed at right angles to the sun's rays for a predetermined period of time (usually in the daytime in summer) to collect heat by using the surfaces 8a as heat collecting surfaces during the predetermined period of time. The surfaces 8a and fin surfaces 8b on the front side are used as heat collecting surfaces during other periods of time, to collect heat.
Generally, in producing cross-fin type heat exchangers, to insure that the fins are spaced apart from one another by a predetermined spacing interval burred openings are formed in the fins, with the burrs of the openings having a height equal to the desired spacing intervals of the fins when the fins are placed one above another in a spaced superposed relationship. This process does not lend itself to stacking fins having burrings of a large height. In this case, the following process is usually adopted. As shown in FIG. 4, fins 12, formed with burred openings 11, are stacked one above another in spaced superposed relationship by dropping the fins 12 to permit the burred openings 11 to be penetrated by guides 14 on a block 13, to provide a stack of fins 12. The fins 12 are then removed from the guides 14 and inserted in grooves 16 formed in an interval setting jig 15, as shown in FIG. 5. Thereafter, the pipes 17 are inserted in the aligned burred openings 11 and expanded into intimate contact with the fins 12, to provide a unitary structure.
This fabricating process raises many problems. Insertion of the fins 12 in the grooves 16 is manually performed, so that the working may be carried out intermittently and become erratic as the fins 12 are stacked and the fins 12 are inserted in the jig. The fins 12 having a relatively small thickness and had no rigidity, so that difficulties are experienced in inserting the fins in the interval setting jig 15 and the operation is time-consuming and requires a lot of labor. Additionally, the fins 12 have a large height and are very unstable because they are usually placed in an upright position, thereby posing the problem of safety in operation.